In a conventional active-matrix type LCD using a liquid crystal panel, the polarity of data signals outputted to data lines is inverted for each frame to drive liquid crystal elements with alternating current to prevent deterioration in the properties of the liquid crystal display. Howevcr, it is known that if the polarity is inverted for each frame, flicker is produced in the image since the voltage which must be applied to a liquid crystal changes depending upon whether the polarity is positive or negative for a frame. To solve this problem, an active-matrix type LCD to which AC drive is applied, uses a method for driving the liquid crystal display based on an electric signal of a polarity different for each data line (that is, each column within the same panel) or a method for driving the liquid crystal based on an electric signal of a polarity different for each scan line (that is, each row within the same panel). An LCD using the driving method in which polarity is inverted for each column is disclosed by, for example, Japanese Published Unexamined Patent Application (PUPA) No.61-275822. An LCD using the driving method in which polarity is inverted for each row is disclosed by, for example, Japanese PUPAs No.61-275823 and No. 62-218943. The method in which polarity is inverted for each row reduces flicker, but involves a problem in that variation in the electric potential of a common electrode of the pixels causes cross talk. The method in which the polarity is inverted for each column has the effect of reducing both flicker and cross talk. However, even if the method is applied, some display patterns may produce flicker and cause cross talk. The construction of an LCD using the method for driving it in which polarity is inverted for each column and the problems associated with it are described below.
FIG. 1 shows the general construction of an LCD using the method for driving it in which polarity is inverted for each column. A gate driver 1 outputs scan signals to n scan lines G1 to Gn. A first data driver 2 is connected to odd data lines D.sub.1 to D.sub.m-1 to which first data signals are outputted. A second data driver 3 is connected to even data lines D.sub.2 to D.sub.m to which second data signals of opposite polarity to that of the first data signals are outputted. TFTs 4 are provided at the respective intersections of the scan lines and data lines, each one of their gate electrodes being connected to a corresponding one of the scan lines, each one of their drain electrodes being connected to a corresponding one of the data lines, and their respective source electrodes being connected to a corresponding one of the pixel electrodes 5 of a liquid crystal cell described below.
The drive operations, set forth below, are described with reference to FIG. 1. Gate signals are sequentially applied to each gate electrode of the TFTs 4, connected to each scan line, by a gate driver I, in response to control signals from a controller (not shown), and the TFTs 4 are sequentially turned on. First data signals and second data signals are applied to respective data lines simultaneously with the gate signals, from the first data driver 2 and the second data driver 3, respectively. The first and the second data signals have opposite polarity. The polarities are inverted for each frame.
Thus, as described above, the first and the second data signals are of opposite polarity. Further, all pixels on the display screen are driven by alternating current so as to be inverted for each data line.
In the conventional LCD, as described above, since the pixels are inverted and driven by alternating current for each data line, flicker and cross talk may be suppressed to some extent, but some display patterns may still cause flicker and cross talk. For example, if each pixel is repeatedly displayed in an on-off pattern of 101010 . . . , flicker occurs since a pixel turned on in one scanning direction is driven by a pulse of the same polarity, even if the pixels are driven by alternating current so as to be inverted for each data line. Further, if the pixel is driven in one scanning direction as described above, a problem exists in that variation in the electric potential of the common electrodes of the pixels causes cross talk.